Auto-injectors have become very popular and have experienced widespread use due to a variety of advantages that they have over typical manual syringe injectors. Essentially, an auto-injector is an automatic injection system which is designed to subcutaneously deliver a specific dosage of a liquid medicament into an individual.
Disposable auto-injectors are typically single-dose delivery devices used for the periodic injection of a drug. Certain epinephrine-containing auto-injectors are a good example of these types of disposable single dose auto-injectors. One removes the cap, removes a safety, and then rapidly presses one end against their thigh. A needle is either exposed or is advanced by the device into the patient and the injection epinephrine automatically begins. The patient will hold the device in place of a prescribed count and then remove and dispose of the device.
Alternatively, an auto-injector can require the user to remove the cap, press the device against the skin, and press a button for the injection to occur. In both types of auto-injector the device automatically shields the needle before and after injection.
IMITREX®, brand sumatriptan, is sold as an injectable in a normal vial in which a syringe needle is inserted through a septum into the vial and a dose is drawn in through the needle (IMITREX Injection single-dose vial (6 mg/0.5 mL) (NDC 01730449-02)). However, it is also available in a second distinct type of auto-injector. It is sold as part of either an IMITREX STATdose System®, 4 mg kit, (containing 1 IMITREX STATdose Pen, 2 prefilled single-dose syringe cartridges, and 1 carrying case (NDC 0173-0739-00)) or an IMITREX STATdose System®, 6 mg kit, containing 1 IMITREX STATdose Pen, 2 prefilled single-dose syringe cartridges, and 1 carrying case (NDC 0173-0479-00)).
In both of these injector systems, a single dose, pre-measured cartridge, including a needle is loaded into the injector before use and the cartridge is disposed of after use. The injector is reusable. There is no way to select a dose—one either has the 4 mg kit or the 6 mg kit. If some other dose is desired, a traditional syringe and vial must be used.
Existing sumatriptan injection devices deliver, without any ability to change the dose, a single dose of a clear, colorless to pale yellow, sterile, nonpyrogenic solution for subcutaneous injection. Each 0.5 mL of commercial sumatriptan injection solution (4 mg) has a concentration of 8 mg/mL of sumatriptan and thus contains 4 mg of sumatriptan (base) as the succinate salt. Commercial formulations also include 3.8 mg of sodium chloride, USP in water for injection, USP. A higher dose is also available wherein each 0.5 mL of sumatriptan injection solution (6 mg) has a concentration of 12 mg/mL and thus contains 6 mg of sumatriptan (base) as the succinate salt. It also contains 3.5 mg of sodium chloride, USP in water for injection, USP. The pH range of both solutions is approximately 4.2 to 5.3. The osmolality of both injections is 291 mOsmol.
The pen-styled design of a syringe is used to deliver multiple doses of a medicament. These devices require the user to set the amount to be delivered, either once or each time they intend to inject themselves. The device may come with a removable and replaceable needle. The user typically “sticks” themselves like they would with any syringe, and then depress the plunger to actuate deliver of the dose. Each dose can be the same, and can be based on such factors as body mass index, or the dose can be variable and based on, for example, a particular blood sugar level. In either event, the pen injector can repeatedly dispense a full dose each time it is used and it is filled such that it can deliver a plurality of doses.
Patent application EP 0713403A1 describes a syringe for administering a fixed volume of liquid pharmaceutical mixtures and generally also other liquids. The syringe is capable of delivering a single dosed in a select range of medicament dosages by first selecting the desired amount of drug to be administered. To avoid the risk of over-dosing or under-dosing, the dose administered by the syringe is pre-set by a physician, medical practitioner, or patient. After the dose amount is selected the syringe must be inserted into a liquid medicament and the desired amount is drawn into the syringe. At this point the device effectively has a fixed volume that can only be used to administer the pre-set dose of the syringe contents to the patient. The structure of the device makes it difficult for a patient to adjust the syringe dose after it has been set even when the syringe is empty. Once the medicament is in the syringe, it is impossible to change from a higher dose to a lower dose without discharging any medicament.
International Application WO2011/111006 describes an auto-injector that allows the end-user to self-administer first and second doses of a medicament. However, the volume of both the first and the second doses are fixed to a pre-set amount of medicament. The end-user cannot choose or adjust the first dose to be administered by the auto-injector. The user cannot take the entire volume of medicament contained in the injector at one time. Instead, a user must take a first dose, remove the injector from the injection site, rotate a knob to re-arm the device, and then reposition the injector at an injection site to receive a second injection.
Application WO2011/045554 describes an auto-injector for use with a plurality of syringes. Each syringe contains a different dose of fluid to be administered. The auto-injector device is a two part housing adapted to receive one of a plurality of syringes. The housing has a spacer that allows the housing to receive syringes containing different doses and administer those doses. While this auto-injector provides certain flexibility in the volume of doses administered in terms of receiving a range of syringe sizes capable delivering a commensurate range of doses, those doses are fixed in the syringe received by the housing.
Another popular type of injection device is a pen-style device. Such pen-type injection devices may contain a dose metering mechanism that administers a dose based on end-user selection. These devices are portable and may be re-useable or disposable.
Such injection devices that allow the end-user to select the administered dose are described, for example and without limitation, in U.S. Pat. No. 5,938,642 ('642 patent). The '642 patent describes an injection pen device with a dose setting mechanism within the housing that incorporates a dial assembly. The end-user can select a dose by rotating the dial. The device is designed to administer multiple doses of a medicament over an extended period of time. The dose of the medicament to be delivered is not pre-set and can be varied over a wide range of doses. The dose selected by the end-user is based on the titration of a known indicator, such as glucose levels in the blood of the end-user when administering insulin. Based on this information, the end-user dials in the requisite dosage.
Although auto injectors that deliver pre-set or variable doses have been used, there is a need for a single-use, disposable device that provides flexibility in the dose delivered, is user friendly in terms of dose selection, yet more reliable in terms of preventing the administration of incorrect doses.